Starting means for supersonic inlet



Jan. 7, 1964 3,116,601

R. E. BARBER STARTING MEANS FOR suPERsoNTc INLET Filed March 28, 1961 2Sheets-Sheet 1 /NVENTOR ROBE. BARBER Jan. 7, 1964 R. E. BARBER STARTINGMEANS FOR SUPERSONIC INLET Filed March 28. 1961 2 Sheets-Sheet 2/lvvENroR ROBERT E BARBER @ZKM/EMM ATTORNEY United States Patent O 3 116601 smarrito MEANS son sUrnRsoNIc nvrn'r Robert E. Barber, Arvada,Colo., assigner to United Aircratt Corporation, East Hartford, Conn., acorporation of Delaware Filed Mar. 28, 1951, Ser. No. 98,882 1 Claim.(Cl. Gil-35.6)

This invent-ion relates to supersonic or hypersonic inlets and moreparticularly to means for swallowingthe shock or starting xed-geometryinternal-compress1on inlets.

The use of air-breathing power plants in systems. operating :at Mechnumbers |above two is limited by inlet performance. There yare twogeneral types of supersomc inl-ets which may be employed,variable-geometry. and ixed-geometry inlets. The use of lixedageometryinlets is desirable because of their lower weight and mechanicalsimplicity as compared to variable-geometry tin-lets; however, theperformance of a hired-geometry inlet 1s genenally poorer than theperfonmance of a variable-'geometry inlet at the same ilight conditions.The performance of fixed-geometry inlets can be improved by internalcompression but internal-compression inlets require boosting to a givenMlach number before the inlet will start (before supersonic ilow ywill:be established in the inlet). This invention provides a system whichwill increase performance of ixed-geometry internal-compression inletsat supersonic speeds.

This invention will increase the performance of an inlet by allowing -aparticular inlet to start at a lower Mach number than it normally wouldstar a-t without this inven-tion, providing reduced boosterrequirements. if it were :desired to start .the inlet lat some lixedMach number, this invention would provide la higher total pressurerecovery by allowing a greater internal compression (contraction ratio)with the inlet utilizing this invention than 1an inlet without thisinvention.

A primary object of this invention is to provide a sh0rtdurationinjection of cooling fluid suela as water which is introduced into theinlet yairllow before the inlet starts (this water is injected upstreamof the inlet throat) after the inlet starts the water low is stopped.

A further object of this invention is 'to provide a simple aontrol whichwill inject the cooling iluid into the inlet t'uct when a predeterminedMach number has been' reached land then lautomatically stop the iluidinjection after Lthe inlet has been started 1 These and other objects ofIthis invention will become readily apparent from the following detaileddescription ,of the `drawings in which:

FlG. l is a schematic illustration of van airabreathing l power planthaving a booster rocket connected 'to the aft end thereof;

FIG. 2 is an enlarged detailed cross-section of a part of a typicalsupersonic inlet illustrating the coolant inje'otion system of thisinvention; and FIG. 3 is a schematic block diagram of a typical controlsystem.

Referring to PEG. 1, an lair-breathing power plant is schematicallyillustrated at 1? as having an inlet generally indicated at 12. Theinlet includes `a conical spike 1-4 and a forwardly directed opening 16.The power plant ill includes, among other well-known details (omittedfor convenience), ian exhaust nozzle 18.

A booster rocket 2li or other suitable power source may be provided toboost the vehicle and the power plant lll to its starting Mach number.

The operating speed of the vehicle or the speed of the relative airapproaching the inlet 12 is contemplated as being in the range of MachNo. t0 Mach No. l0 where this invention will be particularlyadvantageous.

According to this invention, it is intended that where a Patented Jan.7, 1964 ICC Xed-geometry inlet has been designed for a particular Machnumber or limited range of Mach number operation it is desirable to beable lto start the inlet (i.e., to have the shock shlallowed), so thatsupersonic ow is obtained internally of the inlet to ya pointapproximately `at the inlet throat. The flow shocks down at this pointto a snbsonic stream which then lows to the power plant. Once the shockis swallowed or the inlet started, high pressure recovery is obtainedwithin the inlet. The need for obtaining of Ihigh pressure recovery iswell known in the ant and need not be elaborated on here.

lt is the purpose of this invention to inject a small burst or programedamount of coolant such as water into the inlet prior 'to its attainingits design free-stream Mach number so as to start the inlet sooner thancould normally be obtained without resorting to variable-geometryconfigurations. Thus, for example, `as seen in FIG. 2, the inlet cone-14 includes a continuing aft portion 24 which forms the inner wall ofAan annular inlet duct 26. A `suitable outer Cowling 28 is provided andmay support a wall 3b forming the outer Wall of the annular duct 26.Although the coolant injection may take a number of suitable forms, asshown herein, inner and outer high pressure water lines 34 and 36 areprovided. Any suitable high pressure source may be used. Line 34includes va `high-speed valve S, while the line 36 includes a highspeedvalve lil which can control the flow of fluid through la number ofnozzles --42 and 44, respectively.

The valves 33 and 4d may be operated by Ia control of the type shown inFlG. 3 so that coolant is injected into the -inlet duct 26, and when theshock has been swallowed or the inlet started suit-able sensing andsignal devices will shut oit the supply of cooling fluid. The injectedwater cools the airstream while the state of the water chlanges tosuperheated steam. The water injection has the advantageous eiiectdescribed above because the contraction of the airstream, due tocooling, is greater than the expansion of the water which is turned intosteam. This expansion and contraction results in the volume llow of thecooled mixture being less than the volurne ilow of the uncooled lair.The mixture total pressure is 'also slightly greater than the air totalpressure. The effectiveness of this method is dependent on the totaltemperature of the `airstream since no advantage is attained by waterinjection after the air is cooled to near the water temperature.Therefore, the most advantageous results attained at hypersonic flightspeeds; Le., at Mach 6.9, altitude of 37,000 ft., the total temperatureis approximately 3200 R.

It can theoretically be shown that for a fixed-geometryexternal-plus-internal-compression inlet designed for starting at Machnumber 6, with a 'waiter injection weight low of 1/2 the inlet airflow,ie., if the airow in the inlet is 5 lbs/ sec., the water injection raterequired is approximately 2.5 lbs/scc., the inlet designed for startingnormally at Mach number 6 can be started for example at a Mach number of5. lt is also possible to theoretically show that an inlet designed tostart a-t Mach 6 without this invention can be redesigned to utilizethis invention (still starting at Mach 6) and because of .the increasedinternal contraction allowable the total pressure recovery can beincreased, for example, (from 49% to 59% with the same injection rate asmentioned above.

FIG. 3 illustrates a schematic block diagram of a control which might beutilized for the water injection sys tem. Thus a probe Sil provides asignal for the free stream Mach number which signal is conducted to asuitable ,on-ott switching .device 52. A second probe l senses the Machnumber in the inlet, and this signal is conducted to a second on-oitswitching mechanism 56. By example, the switching mechanism 52 isintended to be nor sally open when the free str-:ain signal is bclowMach nun: er 5, while the switching mechanism 56 is intended to benormally closed when the inlet Mach nurnber, for exemple, is below 2.rThus two conditions must exist before both switches are closed. Hence,when the free stream vel city reaches a Mach number of 5, the switchingmechanism 52 `will close so that with the switch 56 also closed thecircuit or loop 6G wiil be energized so that a normally closed solenoidvalve or other suitable device 62 will be opened. Sudden opening of thevalve will permit tlow of cooling iluid from the source 64 through thevalve 62 and then to the inlet duct via a line 66. Gnce the shock hasbeen swallowed and the Mach number in the inlet rises, the switch 56will be opened and the valve 6P. will be automatically closed. Thus itcan be seen that the water is injected only for a very short period,which may be in the order of one second until the inlet starts and thenthe supply is cut oli. The valve 62 may be spring loaded toward a closedposition so that once the 110W of current is interrupted `the valve willcut the supply of coolant.

Although various schematic devices have been shown in HG. 3 fordetecting the starting of the inlet or the positioning of the shocktherein, other sensing devices may be used, as for example, the typeshown in Patent No. 2,971,329, issued February 14, 1961, to F. W. Barryend Patent No, 2,971,330, issued February 14, 1961, to I. W. Clark.

Although only one embodiment of this invention has been illustrated anddescribed therein, it will be apparent that various changes andmodifications may be made in the construction and arrangement of thevarious parts without departing from Athe scope of this novel concept.

What it is desired to obtain by Letters Patent is:

A xed geometry air inlet adapted to operate in a supersonic airstrcaxnand at a ygiven supersonic velocity, means for starting the inlet atalower supersonic velocity han said given velocity comprising a source ofcooling iluid under pressure, `a conduit for conducting i'iuid from aidsource into the interior of said inlet, fast-acting valve means in saidconduit for regulating the flow between said Isource and the interior lsaid inlet including first and second switches in series, a first signalgenerator responsive to vthe free stream Mach number for controllingsaid first switch, la second Isignal generator responsive to the Machnumber in said inlet for controlling said second switch, said iirstswitch being normally open until said ifree stream Mach number reaches arelatively high predetermined value but below seid given supersonicvelocity, and said second switch being normally closed until said inlet.Mach number reaches a predetermined supersonic Mach `number below saidpredetermined Mach number, said first switch closing upon reaching saidgiven Nach number to open said valve means to inject a burst of cloolingfluid into said inlet to cause the latter to start, und said secondswitch opening upon the inlet Much number reaching said predeterminedMach number to close said valve and cut ott said burst of cooling iluid.

References Cited in the file of this patent UNITED STATES PATENTS2,870,601 Demetriades Jan. 27, 1959 2,874,537 Scarborough et al. Feb.24, 1959 2,957,308 McMurtrey etal Oct. 25, 196() 2,997,843 Arnett et al.Aug. 29, 1961 3,001,364 Woodworth Sept. 26, 1961 3,028,731 Drake Apr.10, 1962 3,629,600 Young Apr. 17, 1962

